The present invention relates to the braking of spools, bobbins or the like which are journaled for rotation and which carry elongated stock such as ribbon, wire, threads, cords and the like which elongated stock can be wound upon or paid from such a spool and whereby a torque transmitting connection can be made between such a spool, drum, bobbin or the like and a driven shaft so that on positive driving the empty spool elongated stock can be rewound onto it.
The braking of a spool as envisioned by the invention includes the utilization of the force exerted by an electromagnetic field for producing a brake torque and momentum whereby an armature is used in form of a metallic annulus or ring which can be moved against the force of a spring and is arranged on a flange side of the spool; a magnetic field is closed through that ring when a suitably positioned electromagnet is energized.
In many instances including textile machines, stranding machines, unstranding machines or the like it is necessary to brake spools from which elongated stock is paid. The stock as stated may be comprised of ribbons, wires, threads etc. The braking is primarily a slow-down action with the goal in mind that the stock as it is paid and run off under a constant or near constant tension. Absence of such constancy may lead on one hand into a beating and lateral deflection action which obtains under tension. While on the other hand excessive tension may lead to tearing of the stock.
Brakes are known e.g. through the German printed patent application 15 38 579 using an electromagnet to obtain the requisite brake force. In addition, on unwinding the overall effective spool radius decreases which is effective in a change of the rotational speed of the spool. An analogous indicator is the weight of the spool and all these factors are available as indicators to reduce e.g. the braking force in order to obtain constant tension conditions. However, cases exist which do not only require to slow down the spool as it is uncoiled but the brake should double up as a coupling if subsequently the coil or spool after having been empty is to be reused and fresh ribbon, wires etc. are wound onto the spool. Here the known structure may not be sufficient to cover the complete range of torque necessary for winding and coiling while on the other hand on uncoiling the force should be controlled in such a manner that interference from uncoiling obtains.